A pyro-metallurgical process for treating iron ore concentrates and iron sands recovers pig iron as well as offers the potential for recovering titanium oxides from the slag. The method requires agglomeration of iron ore or iron sand concentrate with a suitable reductant (e.g., finely ground coal) to form compact agglomerates which are the feed material to a natural gas/oxygen enriched air fired smelting furnace, or a natural gas/oxygen fired furnace.
The agglomerates are melted to form hot metal, principally pig iron, with a slag containing oxides of titanium as well as other mineral species associated with the iron sands concentrate, gangue and coal ash. The hot metal is periodically tapped from the natural gas smelter and cast into solid pig iron to be reclaimed and sold as a merchant product. The slag is also periodically tapped from the smelter, quenched with water, and stockpiled. Slag produced from titania-containing iron concentrates can be subsequently processed to recover secondary TiO2 product at a later point in time. The method of TiO2 recovery from the slag incorporates a low to medium temperature process roast to convert the oxide specie to a compound (typically a chloride salt) that can be dissolved in a solvent (preferably water) and then subsequently precipitated as a pure solid using solvent extraction techniques.
The agglomerates can be either charged ‘cold’ to the natural gas smelter, or pre-heated in a agglomerate pre-heater and then charged ‘hot’ (up to 1200° C.). Process off-gas from the smelting furnace can be tempered and cleaned, either hot using a hot cyclone, or cooled to near ambient conditions using evaporative cooling methods or scrubbed using a direct contact water scrubber. Cleaned hot smelter off-gas can utilized directly in the pre-heater. Cool, cleaned smelter off-gas can be compressed and then utilized in the agglomerate pre-heater. Furthermore the agglomerate pre-heater fuel can either be 100% hot smelter off-gas, 100% natural gas, or some portion of natural gas that is mixed with the conditioned smelter off-gas (either hot or cooled). This results in achieving a high level of energy flexibility and efficiency for the overall process, thereby minimizing the OPEX (operational expenditure) utility cost (primarily natural gas), especially when site specific conditions for the commercial plant are considered. The spent exhaust gas from the agglomerate pre-heater retains sufficient temperature and sensible heat to act as the drying medium for drying the raw sand for the concentrating plant.